SMB external storage GUI error?

I’m exploring nextcloud 17 in docker container.
Now I’m trying to set up external storage with my SMB share (not matter which kind)
I can create share using cmd like that:
sudo -u www-data php occ files_external:create myshare 'smb' password::sessioncredentials -c host= -c share=Public -c root=/ -c domain=mydomain
and it work as expected and it shown in GUI

But if I simply press “save” in GUI - I got error…

but nothing has not changed…